1. Field of the Invention
A chemical preservative and lubricant for processing animal feedstuffs into pelletized feed that enhances milling efficiency, inhibits fungi, bacteria, and mycotoxins from growing in finished products even if they have relatively high water content, and which does not release objectionable amounts of butyric acid into the air from the finished product.
2. Discussion of the Background
It is common practice to use fungicides in animal feedstuffs containing propionic acid or its sodium, calcium or ammonium salt in some form. Bland et al., U.S. Pat. No. 5,547,987, discloses a composition for inhibiting pathogen growth in animal feeds using a mixture of butyric acid and propionic acid, each acid partially or completed converted to one of its salt forms. n-Butyric acid has an objectionable smell and therefore is difficult to formulate into commercially acceptable products. Many salts of n-butyric acid are less malodorous than the free acid but are still objectionable to users and to livestock eating the treated feed. Prior to Bland et al., neither n-butyric acid nor its salts were considered to have practical utility as feed preservatives.
Huitson et al, U.S. Pat. No. 3,595,665, discloses a method for preventing mold growth in crops and animal feedstuffs during storage based on binary and ternary mixtures of lower carboxylic acids.
Herting et al, Cereal Chem. 51:382-388 (1974), reported that isobutyric acid is the most effective antifungal agent among the common C1-C4 acids and that mixtures such as propionic:n-butyric:water (25:25:50) and propionic:isobutyric:water (25:25:50) are more effective than the individual acids in water. It was found that activity depended on the amount of water in the mixture; surprisingly, the activity increased as the proportion of water was increased. However, the presence or absence of mold was determined visually which is too imprecise method to draw valid conclusions.
Skov et al, U.S. Pat. No. 4,183,953 added isobutyric acid to aqueous ammonium isobutyrate in order to lower the crystallization temperature, enabling the use of ammonium isobutyrate solutions in unheated areas in cold weather. The relative antifungal activities of ammonium isobutyrate alone vs. isobutyric acid/ammonium isobutyrate were not reported.